The present disclosure relates to a touch panel used in a screen-input-type display apparatus and the like and a method of producing the touch panel.
For example, a touch panel of an analog resistive film system that detects input coordinates based on an amount of a resistance change includes a pair of an upper transparent substrate and a lower transparent substrate that are opposed to each other with a predetermined gap therebetween, resistive films provided on opposed surfaces of the pair of the transparent substrates, connection terminals electrically connected to the resistive films, and a wiring substrate electrically connected to the connection terminals. In the touch panel, a coordinate value is detected based on a resistance value between the resistive films that are brought into contact with each other by a pressing force applied from one substrate surface, and an output terminal.
The connection terminal electrically connected to each of the resistive films that are provided on the transparent substrates is provided on, for example, the same substrate as the transparent substrate on which the resistive film to be connected is provided. That is, the upper connection terminal is provided on the upper transparent substrate, and the lower connection terminal is provided on the lower transparent substrate. Patent Document 1 discloses a terminal structure in which the upper connection terminal and the lower connection terminal are not superimposed in plan view. The upper connection terminal and the lower connection terminal are connected to one surface side and the other surface side of the wiring substrate by bonding, respectively. Further, it is also structured by performing bonding between the wiring substrate and the transparent substrates in the same layer as a bonding layer such as an anisotropic conductive film that connects the wiring substrate and the connection terminals by bonding.
Patent Document 1: Japanese Patent Application Laid-open No. 2002-182854 (paragraphs [0012] and [0040] to [0042], FIG. 1)
However, in a case where the upper connection terminal and the lower connection terminal are not superimposed in plan view and the upper connection terminal and the lower connection terminal are connected to one surface side and the other surface side of the wiring substrate by bonding, respectively, there are generated air gaps between the wiring substrate and the transparent substrates, and therefore a gap formed between the two transparent substrates in an area where the wiring substrate is disposed cannot be kept to a desired thickness. As a result, the gap formed between the substrates cannot be made uniform in the substrate plane, which causes a problem that Newton's rings and inputting errors of a touch panel occur.
Moreover, even when the transparent substrates and the wiring substrate are bonded by the bonding layer such as an anisotropic conductive film that bonds the wiring substrate and the connection terminals so as to fill a space between the transparent substrate opposed to the transparent substrate on which the connection terminals are provided and the wiring substrate, it is difficult to stably produce a touch panel such that a gap between the two transparent substrates in the area where the wiring substrate is disposed is always kept constant, due to variation in thicknesses of the wiring substrate, the bonding layer, the connection terminal, and the like, which still causes a case where Newton's rings and inputting errors occur.